1. Technical Field of the Invention
This invention relates to testing and analyzing a communications network. More particularly, the invention relates determining network discrete utilization.
2. Background Art
Users and managers of communications networks are interested in the capacity, performance, reliability, availability, topology, service level attainment, and modeling of their networks. Currently, many separate, incompatible, complicated, and often unsatisfactory tools are required to perform the tasks required by network managers.
One prior art technique provides for communication system analysis in which sequences of pings of different sizes are sent, transmitted in isolation from each other, in order to determine characteristics of the network beyond availability of resources and “usual” response time. In accordance with this technique, the best and mean times for the sequences of pings of different lengths are measured, and then the following are geometrically derived via use of the test ping packet sizes and the reciprocal of the bandwidth slope:                the network path's bandwidth,        the network path's propagation delay, and        the network path's queuing time.Further network testing involves sending bursts of pings to determine the loss rate of packets, from which the “internal packet size of the network” can then be determined. By this it is meant that the minimum device buffer size in the transmission path of the network can be discovered. The sending of bursts of pings of decreasing size is also described, the intent of which is to determine if smaller packets are prioritized over larger packets. In this way, the following is determined:        the network path's minimum buffer size (also referred to as “internal packet size”); and        the network's short frame prioritization capability.        
It is recognized in the art that there will generally be a plurality of network hops between the test station and the remote station, each with its own bandwidth. In these circumstances, taking the reciprocal of the slope of the line representing bandwidth is equivalent to saying that:(1/Bandwidth)=(1/b1+1/b2+ . . . 1/bn)where b1, b2, . . . . bn are the bandwidths of all the hops in the path. This will produce a bandwidth close to accurate only if there is one hop in the path that is significantly slower than all the others. Where this is not the case, the estimate may be inaccurate because no account is taken of the fact that for a multi-hop path, the intermediate nodes will delay onward transmission of a packet until the whole packet has been received.
U.S. patent application Ser. No. 09/267,843 filed 12 Aug. 1999 by F. K. P. Klassen and R. M. Silverman for System and Method for Analyzing and Tuning a Communications Network (Klassen and Silverman), and Ser. No. 09/452,403 filed 1 Dec. 1999 by K. Chan, F. K. P. Klassen, and R. M. Silverman for System and Method for Monitoring Performance, Analyzing Capacity and Utilization, and Planning Capacity for Networks and Intelligent, Network Connected Processes (Chan, Klassen and Silverman) improved upon the then existing art by:                distinguishing between and calculating the values for the streaming and discrete speeds of the network; and        calculating the utilization of that connection.The distinction between the discrete and streaming speeds of a network allows for two accurate measures of network speed across multiple hops, as opposed to the previously known one, potentially inaccurate measure.        
The discrete speed reflects the network's maximum bandwidth for handling “conversational” type transaction traffic, such as query-response. The streaming speed reflects the network's maximum speed for “batch” type traffic, such as file transfers and print. The network's streaming speed can also be referred to as “network throughput bandwidth.”
Thus, probative test packets are transmitted, received and time stamped, and then mathematically analyzed. The result is a system and method in which full network capacity analysis can be performed across networks of any size, including the Internet, and to do so with no need for network documentation or knowledge of network topology or knowledge of capacity of network components.
It is an object of the invention to provide an improved system and method for determining end to end network discrete utilization, as distinguished from network streaming utilization.
It is a further object of the invention to provide an improved system and method for tuning the network.
It is a further object of the invention to provide an improved system and method for estimating the network's current performance and its future performance under changed conditions (“what-if” scenarios).